A product has a characteristic value, which indicates a predetermined characteristic and is measured before shipment, and is discriminated as a non-defective article or a defective article depending on whether or not a predetermined standard is satisfied. The product is discriminated by comparing the characteristic value of the product measured using a product discriminating device and an inspection standard, of which condition is stricter than a product standard (characteristic value required for the product). If the variation in the measured characteristic values of the products is only the variation in the characteristic values of the products themselves, whether the product is a non-defective article or a defective article can be correctly discriminated by the product discriminating device even if the inspection standard is defined in the same condition as the product standard.
However, the variation in the measured characteristic values of the products includes not only the variation in the characteristic values of the products themselves, but also the variation in the measurement values of the measurement system. Thus, the products discriminated as non-defective articles by the product discriminating device may include a defective article, or the products discriminated as defective articles may include a non-defective article. A probability a product, which is a defective article, is mistakenly determined as a non-defective article is called a consumer risk, and a probability a product, which is a non-defective article, is mistakenly determined as a defective article is called a producer risk.
A method of calculating the consumer risk and the producer risk is disclosed in Non-Patent Documents 1 and 2. Non-Patent Document 1 discloses a method of calculating the consumer risk and the producer risk by a product discriminating device using the Monte Carlo method. Non-Patent Document 2 discloses a method of calculating the consumer risk and the producer risk assuming that the variation in the characteristic values and the variation in the measurement values have normal distributions using a double integral equation.
Non-Patent Document 1: M. Dobbert, “Understanding Measurement Risk”, NCSL International Workshop and Symposium, August 2007.
Non-Patent Document 2: David Deaver, “Managing Calibration Confidence in the Real World”, NCSL International Workshop and Symposium, 1995.